A new fluorescence band obtained by the excitation of plants at 280 nm and its implications to the remote assessment of vegetation

Intact vegetation when excited at 280 nm produced two convoluted broad band fluorescence emissions; the first centered at 340 nm, and the second centered at 440 nm. Strong similarities were noted between the fluorescence excitation and emission spectra of intact vegetation and pure ribulose 1,5-bisphosphate carboxylase (rubisco) which constitutes 40% of the soluble plant proteins. In addition, similar fluorescence characteristics were observed for proteins and polypeptides containing the aromatic amino acids; tryptophan (TRP), tyrosine (TYR), and phenylalanine (PHE). As a result, rubisco along with plant proteins and polypeptides containing aromatic amino acids are believed to contribute to the convoluted fluorescence emission with a maximum at 340 nm. These fluorescence maxima are discussed along with their implications in distinguishing species and the remote assessment of nitrogen deficiency of agronomically important crops.